SPINACH Spinacia oleracea

FAMILY CHARACTERISTICS
    Many plants are harvested for the use of their leaves. Leafy plants are referred to as greens or potherbs and include spinach, kale, collards, and mustard. Swiss Chard (Beta vulgaris L. subsp. cicla) and beets (Beta vulgaris L. subsp. vulgaris) are in the same family and the leafy foliage of these plants are consumed in the same way as members of thespinach family.  Other common plants in the spinach family are the sugar beet, lambs quarter, and glasswort.  The plants in this family are dicotyledons.  There are about 102 genera and 1,400 species in the world.  The plants are similar in characteristics, usually having alternate and simple leaves. The inflorescence is cymose, often bracteate, and flowers are small and inconspicuous.  Many of the plants in this family are thought to have originated in southwestern Asia and were introduced into Europe in the Middle ages.  European settlers brought members of this family to N. American as they settled in the New World.
    Family members include:
        Atriplex hortensis L., Orache
        Beta vulgaris L., Beet
        Beta vulgaris L. (Cicla group), Chard
        Chenopodium bonus-henricus L., Good King Henry,  Mercury
        Spinacia oleracea L., Spinach

   CROP HISTORY AND DEVELOPMENT
 Spinach was cultivated over 2,000 years ago in Iran.  Cultivation of spinach began during the Greek and Roman civilizations.   Our name for spinach is derived from the Persian ward "ispanai" which mean "green hand" whcih later became "spanachia"(Late Latin), to spinach and spinach and spinage(English).  The Arbs named it ‘the prince of vegetables’.  In 647 A.D. spinach was introduced into China and was then transported to Spain in 1100.  The prickly seeded form was known in Germany in the 13th century and the smooth seeded form was not described until 1552.  It is the smooth seeded form that is used today in commercial production.  By 1806, spinach had become a popular vegetable and was listed in American seed catalogs.  In the 1920’s the U.S. pushed spinach commercially, with Popeye the Sailorman cartoon being a great advacate in spinach consumption.
    Spinach is used as a leafy green and eaten raw in salads.  It is also used as a cooked green (potherb) much like turnip greens or collard greens.
    Nutritional Constituents  Spinach contains large amounts of minerals and vitamins, especially vitamin A, calcium, phosphorus, iron and potassium.  Spinach also has high levels of  protein.
    Ninety-one percent of spinach weight is water. A serving of spinach contains 3.2 grams of protein, 4.3 grams of carbohydrates, and 0.3 grams of fat. It also contains Vitamin A, and C, thiamin, riboflavin, and niacin. Calcium, phosphorus, iron, sodium, and potassium are also found in spinach greens.

Production  Spinach is grown across the US from California to Florida.  California is responsible for over one half of the production in the US. Texas is also a large producer of spinach, about one third of the total crop in the US.  Colorado, Florida and New Jersey also have significant acreage.      California is a leader in the processing industry, producing over one third of the total US production.  Arkansas and Oklahoma produce the remaining of the processed spinach.

    Cultivars and Varieties  It is important to choose the proper variety for disease and insect resistance.  It is also important to choose a variety that will be adequate for the season in which it will be grown.  If growing in the late spring or summer, slow growing and slow bolting varieties are preferred.  If growing in the fall, winter, or early spring, fast growing varieties should be used.  There are three types of spinach: the smooth leaf, the savoyed leaf, which is the traditional Eastern style with a textured appearance, and the semi-savoyed, used for fresh market or processing.  The smooth leaf and semi-savoy are used mainly for processing, while the savoy is used for fresh market.  The savoy types are better for shipping because they are less likely to wilt or turn yellow before reaching the market.  The smooth leaf are easier to clean and remove soil from leaves before canning or freezing for processing.
    Smooth Leaf Types-
         'Denali' (F1)- 36 days, white rust and mildew tolerant, moderately slow bolting.
         'Hector' (F1)- 37 days, downy mildew resistant. Ideal for salad.
         'Space' (F1)- 39 days, high yielding, downy mildew resistant. Good greenhouse performer.
    Semi-savoyed Leaf Types-
        'Melody' (F1)- good for spring and fall crops, downy mildew and cucumber  mosaic virus resistant
        'Coho' (F1)- 37 days, white rust tolerant, moderate bolt tolerance
        'Indian Summer' (F1)- good greenhouse performer, cucumber mosaic virus and downy mildew resistance.
    Savoy Leaf Types-(textured appearance)
         'Tyee' (F1)- 42 days, the most bolt resistant savoy type.
         'Vienna' (F1)- upright, good for spring and fall plantings. Some downy mildew resistance.
         'Savoy Hybrid'-  good fall crop for shipping and freezing.  Resistant to downy mildew and cucumber mosaic virus.
    Specialty Type-  'Tetragonia' (Tetragonia tetragonioides) (New Zealand Spinach) 50 days.  Spinach like plant that tolerates hot weather better than spinach.  It is actually a warm season crop and must be planted after the danger of frost is over. 'Tetragonia' is native to New Zealand , Japan, and Australia.  It was introduced into England in the 1700’s. The seeds are very slow to germinate so they should be soaked before planting.  It will grow 2 or more feet with a spreading, branching habit of 4-6 feet.  The New Zealand spinach does not have any disease or insect problems of consequence.
    Processing Spinach- 'Seven R' - semi-savoy type.  Plants are large and grow quickly.  It is good for mechanical harvesting and processing.  It has resistance to downy mildew.
    Greenhouse Spinach- Spinach can be grown hydroponically in the greenhouse.  The cultivars 'Indian Summer' and 'Space' are two good types that do well in the greenhouse.

PLANT CHARACTERISTICS
    Overview.  The spinach used for fresh market, processing and greenhouse, are all of the same species, therefore have the same plant characteristics.  Spinach is a cool season annual herb.  It can survive severe frosts in the winter.

Root System.  Spinach has a taproot that is deep and has branching roots in the top 6-10 inches of soil.  These roots can extend to several feet, but the feeder roots remain in the top 2-4 inches of the soil.  The system is generally thick and shallow.      Stem and Leaves.  Spinach is a fleshy leaf annual that grows in a rosette.  The leaves are glabrous (non-hairy), broad and tender.  The leaves may be savoy (puckered or crinkled), semi-savoy, or smooth. The leaves are lobed at the base and sometimes lobed on the sides.  The stem is edible as well, but tougher than the leaves.  The stem is the development of the reproductive stage.  The branching seed stalk and pointed leaves develop on the central stem.

    Flowers and Fruit.  The plant can bear either male or female flowers on the same plant.  Sex expression varies, the plants are primarily dioecious.  The flowers are inconspicuous, greenish-white, and are borne in clusters on a spike.  The female flowers develop into seed like fruit.   Male plants usually bolt faster than female.  The flowers are wind pollinated.  Spinach becomes reproductive in response to the day length and temperature conditions. As day length reaches 15 hours, the development of the seed stalk takes place and is accelerated in 40-50°F temperatures. The seed stalk is hollow and can reach 4-5 feet high.

Seed.  There are about 90 seeds per gram, 2,500 seeds per ounce, and about 40,000 seeds per pound.  It takes about 8 days for seed to germinate. Seeds should be planted between ½ to 1 inch deep.  One acre requires between 10-15 pounds of seed for direct seeding.  The plant turns yellow as the seeds are reaching maturity.  The seed are round or prickly depending on the cultivar selected.

PROPAGATION METHODS
    Temperatures.  Spinach is classified as a  hardy cool season crop.  It can be grown most anywhere in the US, but does best in 50-60°F temperatures.  It will not germinate well in hot weather; if soil temperatures exceed 85°F the seeds may become dormant.
    Direct seeding.  Transplants are not used commercially, but are good for home gardens.  All commercial production is direct seeded with little or no thinning.  The seed is either broadcast or sown in rows on wide beds.  There should be 2-6 inches in between plants in the row. The distance between rows should be 12 to 36 inches. Spinach seeds need consistent soil moisture for proper germination.  Being a cool season crop, the seed should be sowed when the ground is cool in early spring.  For a fall crop, the seed can be sown from July to September.  Seeding time for the coastal plain is February to March, and mid-August to late October,  in the Piedmont, from late February to early April and from August to mid-October, and in the mountains, from March to April and mid-July to mid-September.

CULTURAL PRACTICES

Overview.  Spinach has two stages in its life cycle;  the vegetative, rosette stage and the bolting, seed stalk stage.  It is important that the plants be maintained to avoid bolting.  Once the plant bolts it is no longer marketable.  The first stage is relatively short (about 35-40 days) and must be watched very closely to maintain good quality.      Soils. Spinach can grow in a range of soils as long as they are moist and fertile. Fertile, sandy loams, high in organic matter is recommended.  The plants are sensitive to acidity and the soil should be at least a pH of 6.0, with an optimum pH of 6.2-6.9.  The symptoms of low pH are low germination, yellowing and browning of the margins and tips of seedling leaves, browning of roots, general slow growth, and even the death of the plant.      Fertility.  Spinach from the field should be tested for nutrient levels by collecting about 15 of the most recently fully developed leaves.  When the plant is 30-50 days old, the nitrogen levels should be around 4.0-6.0%, phosphorus 0.3-0.6%, potassium 5.0-8.0%, and calcium 0.7-1.2%. Before planting in early

Spinach bolting

spring, 85-125 lbs N, 75-85 lbs P₂0₅, and 85-125 lbs K₂0 should be added to the soil, depending on soil test results.  If the fertilizer is added during seeding it should be banded 2-3 inches below the seed and 6 inches to the side.  The fertilizer should not come in contact with the seed.
    Weed Control.  Cultivation is done in spinach fields, but it should be shallow as to not harm any of the roots.  Spinach does not compete well with weeds. Usually 2-4 cultivations are sufficient during the growing season.
    Irrigation.  With the root system being mostly shallow, spinach does best in uniformly moist conditions.  Fields are irrigated by either flooding, furrow, or overhead sprinklers.  An application every 7-10 days of 1 inch of water is recommended during dry periods without rainfall.  Overhead irrigation can reduce yields by increasing the risk and levels of disease because many diseases thrive in moist, humid conditions.  Therefore it is recommended to use furrow or flooding irrigation.  It is important to keep soil moist when seeds are germinating.

INSECTS
    All crops produced are susceptible to insect damage.  Pest management must be carefully controlled in leafy greens.  Any defects in the leafy green causes the quality to decline.  Consumers do not want spinach with insect damage that are portrayed as holes in the leaf.  Unfortunately, for this reason, pesticides are highly used on spinach.  It is important to use pesticides safely, to read the label and wear protective gear.  Insecticides are constantly changing labels, laws, and regulations. It would be beneficial to check with the extension service to find out which insecticides do best in certain areas.
    Green Peach Aphid- (Myzus persicae) is a very detrimental insect to spinach.  It is so dangerous because it can transmit diseases that can wipe out large portions of the crop. The aphid is pale yellowish in color and is small.  It lives mainly on the underside of leaves and therefore is hard to control by spraying.
    Spinach Leafminer- (Pegomyia hyoscyami) this is a serious insect that causes much damage in spinach in many areas across the United States.
    Budworm injury- (Hylemya cilicrura) This is the seed corn maggot.  The larvae feed on young leaves.  The cucumber beetle feeds on older leaf spinach.  The damage found on spinach by both of these insects can usually be found on fresh market spinach.
    Other Insect Pests. Cabbage looper, cucumber beetle, flea beetles, root maggots and cutworms.  The aphid and the leaf minor are cause the most serious damage.

DISEASES
    The quality and marketability of spinach is reduced with even the slightest amount of defects, .
    Downy Mildew-  (Peronospora spinaciae)  This is a fungus that is distributed worldwide and is particularly bad in the southern US and coastal regions.  It causes leaf spotting that detracts from the quality and appearance.  The fungus increases profusely in high humidity.  The spores can over winter in mild climates, but usually blow in from conidia.  The best control measure is the use of resistant varieties.
    Bacterial Soft rot (Erwinia carotovora) is one of the most important diseases.  Its symptoms include water soaked tissue and muddy-green or greasy appearance of leaves.  Rapid decay occurs and the tissue becomes wet and mushy.  This bacteria is found in the soil and in plant debris.  It can enter into the plant through mechanical injury, insect injury, disease lesions and other skin punctures.
    Fusarium Wilt- (Fusarium oxysporum f. sp. spinaciae) is a wilt that is caused by a fungus.  The plants become pale green, the leaf margins roll inward and the plant begins to die.  The fungus is transferred through contaminated seed and soil.
    White Rust (Albugo occidentalis)- Is a fungus that cause white blister-like pustules on the underside of leaves.  They are filled with white spores and the surrounding tissue turns brown and dies.  It occurs most frequently in Texas and the southwestern states.  The fungus favors clear, warm, and dry days with cool nights.
    Other Important Diseases-  Curly top virus- vein clearing on young leaves. The leafhopper is a vector.  Mosaic, caused by the cucumber mosaic virus, transmitted by the green peach aphid.  Young leaves begin to mottle, become yellow and die.  Intensity of the virus increases under long days and intense light.  There are some varieties resistant to these viruses.
    Spinach Blight, Yellows-  Are spread mechanically and by the green peach aphid.  The plants show a light yellowing and malformation of young leaves.

HARVESTING
    Spinach usually matures in 37-70 days, most are within 40-50 days.  Spinach should be harvested before bolting to reduce yellowing, breakage and other leaf deterioration, and to avoid development of the seed stalk.
    Fresh Market-  An acre of fresh spinach will yield 4 to 8 tons/acre, on average 6,000 pounds per acre.  The plant may be harvested from the time there are 5-6 leaves on the plant until right before the seed stalk develops.  After the seed stalk has developed the plant is no longer marketable.
    For fresh Market the entire rosette is cut mechanically at the soil surface.  The plant is then put into bulk trucks or trailers.
    Processing-  The spinach is cut about an inch above the soil surface, allowing regrowth.  Many times, two harvests are possible before the plant develops a seed stalk.  Spinach meant for processing has a higher yield per acre because of the dense planting, an average 13,200 pounds per acre could be expected. Yields vary widely due to seasonal and environmental conditions.

POST HARVEST

Spinach should be held at 32°F and 95 to 100% relative humidity.  Spinach will perish very quickly, and can only be stored from 10-14 days.  When taken from the field, rapid cooling is essential, usually done by a vacuum system, or hydrocooling.  Excess water is removed and then the product is shipped with ice to preserve the freshness.  Much of the spinach for fresh market is put into plastic bags to reduce physical injury and moisture loss.  It is usually packed in 20 lb cartons with 2 dozen bunches.  Spinach can also be sold loose, in bunches or in polyethylene bags.